Performance impact of turning up Max transparency bounces?
No, it has no effect if you do not have any transparent shaders in your scene. Setting it too high could result in a lot of extra bounces being calculated for little result on some stray transparent object. One of those corner cases that comes up sometimes. Additionally, some would say the default of 8 (with no early path termination, since the minimum is also 8) is already a "high" number. It depends on your scene and your goals. Adjust accordingly.